Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2008 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 #ifndef SERIALGC

 // A HeapRegion is the smallest piece of a G1CollectedHeap that

 // can be collected independently.

 // NOTE: Although a HeapRegion is a Space, its

 // Space::initDirtyCardClosure method must not be called.

 // The problem is that the existence of this method breaks

 // the independence of barrier sets from remembered sets.

 // The solution is to remove this method from the definition

 // of a Space.

 class CompactibleSpace;

 class ContiguousSpace;

 class HeapRegionRemSet;

 class HeapRegionRemSetIterator;

 class HeapRegion;

 // A dirty card to oop closure for heap regions. It

 // knows how to get the G1 heap and how to use the bitmap

 // in the concurrent marker used by G1 to filter remembered

 // sets.

 class HeapRegionDCTOC : public ContiguousSpaceDCTOC {

 public:

   // Specification of possible DirtyCardToOopClosure filtering.

   enum FilterKind {

     NoFilterKind,

     IntoCSFilterKind,

     OutOfRegionFilterKind

   };

 protected:

   HeapRegion* _hr;

   FilterKind _fk;

   G1CollectedHeap* _g1;

   void walk_mem_region_with_cl(MemRegion mr,

                                HeapWord* bottom, HeapWord* top,

                                OopClosure* cl);

   // We don't specialize this for FilteringClosure; filtering is handled by

   // the "FilterKind" mechanism.  But we provide this to avoid a compiler

   // warning.

   void walk_mem_region_with_cl(MemRegion mr,

                                HeapWord* bottom, HeapWord* top,

                                FilteringClosure* cl) {

     HeapRegionDCTOC::walk_mem_region_with_cl(mr, bottom, top,

                                                        (OopClosure*)cl);

   }

   // Get the actual top of the area on which the closure will

   // operate, given where the top is assumed to be (the end of the

   // memory region passed to do_MemRegion) and where the object

   // at the top is assumed to start. For example, an object may

   // start at the top but actually extend past the assumed top,

   // in which case the top becomes the end of the object.

   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj) {

     return ContiguousSpaceDCTOC::get_actual_top(top, top_obj);

   }

   // Walk the given memory region from bottom to (actual) top

   // looking for objects and applying the oop closure (_cl) to

   // them. The base implementation of this treats the area as

   // blocks, where a block may or may not be an object. Sub-

   // classes should override this to provide more accurate

   // or possibly more efficient walking.

   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top) {

     Filtering_DCTOC::walk_mem_region(mr, bottom, top);

   }

 public:

   HeapRegionDCTOC(G1CollectedHeap* g1,

                   HeapRegion* hr, OopClosure* cl,

                   CardTableModRefBS::PrecisionStyle precision,

                   FilterKind fk);

 };

 // The complicating factor is that BlockOffsetTable diverged

 // significantly, and we need functionality that is only in the G1 version.

 // So I copied that code, which led to an alternate G1 version of

 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could

 // be reconciled, then G1OffsetTableContigSpace could go away.

 // The idea behind time stamps is the following. Doing a save_marks on

 // all regions at every GC pause is time consuming (if I remember

 // well, 10ms or so). So, we would like to do that only for regions

 // that are GC alloc regions. To achieve this, we use time

 // stamps. For every evacuation pause, G1CollectedHeap generates a

 // unique time stamp (essentially a counter that gets

 // incremented). Every time we want to call save_marks on a region,

 // we set the saved_mark_word to top and also copy the current GC

 // time stamp to the time stamp field of the space. Reading the

 // saved_mark_word involves checking the time stamp of the

 // region. If it is the same as the current GC time stamp, then we

 // can safely read the saved_mark_word field, as it is valid. If the

 // time stamp of the region is not the same as the current GC time

 // stamp, then we instead read top, as the saved_mark_word field is

 // invalid. Time stamps (on the regions and also on the

 // G1CollectedHeap) are reset at every cleanup (we iterate over

 // the regions anyway) and at the end of a Full GC. The current scheme

 // that uses sequential unsigned ints will fail only if we have 4b

 // evacuation pauses between two cleanups, which is _highly_ unlikely.

 class G1OffsetTableContigSpace: public ContiguousSpace {

   friend class VMStructs;

  protected:

   G1BlockOffsetArrayContigSpace _offsets;

   Mutex _par_alloc_lock;

   volatile unsigned _gc_time_stamp;

  public:

   // Constructor.  If "is_zeroed" is true, the MemRegion "mr" may be

   // assumed to contain zeros.

   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,

                            MemRegion mr, bool is_zeroed = false);

   void set_bottom(HeapWord* value);

   void set_end(HeapWord* value);

   virtual HeapWord* saved_mark_word() const;

   virtual void set_saved_mark();

   void reset_gc_time_stamp() { _gc_time_stamp = 0; }

   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);

   virtual void clear(bool mangle_space);

   HeapWord* block_start(const void* p);

   HeapWord* block_start_const(const void* p) const;

   // Add offset table update.

   virtual HeapWord* allocate(size_t word_size);

   HeapWord* par_allocate(size_t word_size);

   // MarkSweep support phase3

   virtual HeapWord* initialize_threshold();

   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);

   virtual void print() const;

 };

 class HeapRegion: public G1OffsetTableContigSpace {

   friend class VMStructs;

  private:

   enum HumongousType {

     NotHumongous = 0,

     StartsHumongous,

     ContinuesHumongous

   };

   // The next filter kind that should be used for a "new_dcto_cl" call with

   // the "traditional" signature.

   HeapRegionDCTOC::FilterKind _next_fk;

   // Requires that the region "mr" be dense with objects, and begin and end

   // with an object.

   void oops_in_mr_iterate(MemRegion mr, OopClosure* cl);

   // The remembered set for this region.

   // (Might want to make this "inline" later, to avoid some alloc failure

   // issues.)

   HeapRegionRemSet* _rem_set;

   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }

  protected:

   // If this region is a member of a HeapRegionSeq, the index in that

   // sequence, otherwise -1.

   int  _hrs_index;

   HumongousType _humongous_type;

   // For a humongous region, region in which it starts.

   HeapRegion* _humongous_start_region;

   // For the start region of a humongous sequence, it's original end().

   HeapWord* _orig_end;

   // True iff the region is in current collection_set.

   bool _in_collection_set;

     // True iff the region is on the unclean list, waiting to be zero filled.

   bool _is_on_unclean_list;

   // True iff the region is on the free list, ready for allocation.

   bool _is_on_free_list;

   // Is this or has it been an allocation region in the current collection

   // pause.

   bool _is_gc_alloc_region;

   // True iff an attempt to evacuate an object in the region failed.

   bool _evacuation_failed;

   // A heap region may be a member one of a number of special subsets, each

   // represented as linked lists through the field below.  Currently, these

   // sets include:

   //   The collection set.

   //   The set of allocation regions used in a collection pause.

   //   Spaces that may contain gray objects.

   HeapRegion* _next_in_special_set;

   // next region in the young "generation" region set

   HeapRegion* _next_young_region;

   // For parallel heapRegion traversal.

   jint _claimed;

   // We use concurrent marking to determine the amount of live data

   // in each heap region.

   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.

   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.

   // See "sort_index" method.  -1 means is not in the array.

   int _sort_index;

   // Means it has (or at least had) a very large RS, and should not be

   // considered for membership in a collection set.

   enum PopularityState {

     NotPopular,

     PopularPending,

     Popular

   };

   PopularityState _popularity;

   // <PREDICTION>

   double _gc_efficiency;

   // </PREDICTION>

   enum YoungType {

     NotYoung,                   // a region is not young

     ScanOnly,                   // a region is young and scan-only

     Young,                      // a region is young

     Survivor                    // a region is young and it contains

                                 // survivor

   };

   YoungType _young_type;

   int  _young_index_in_cset;

   SurvRateGroup* _surv_rate_group;

   int  _age_index;

   // The start of the unmarked area. The unmarked area extends from this

   // word until the top and/or end of the region, and is the part

   // of the region for which no marking was done, i.e. objects may

   // have been allocated in this part since the last mark phase.

   // "prev" is the top at the start of the last completed marking.

   // "next" is the top at the start of the in-progress marking (if any.)

   HeapWord* _prev_top_at_mark_start;

   HeapWord* _next_top_at_mark_start;

   // If a collection pause is in progress, this is the top at the start

   // of that pause.

   // We've counted the marked bytes of objects below here.

   HeapWord* _top_at_conc_mark_count;

   void init_top_at_mark_start() {

     assert(_prev_marked_bytes == 0 &&

            _next_marked_bytes == 0,

            "Must be called after zero_marked_bytes.");

     HeapWord* bot = bottom();

     _prev_top_at_mark_start = bot;

     _next_top_at_mark_start = bot;

     _top_at_conc_mark_count = bot;

   }

   jint _zfs;  // A member of ZeroFillState.  Protected by ZF_lock.

   Thread* _zero_filler; // If _zfs is ZeroFilling, the thread that (last)

                         // made it so.

   void set_young_type(YoungType new_type) {

     //assert(_young_type != new_type, "setting the same type" );

     // TODO: add more assertions here

     _young_type = new_type;

   }

  public:

   // If "is_zeroed" is "true", the region "mr" can be assumed to contain zeros.

   HeapRegion(G1BlockOffsetSharedArray* sharedOffsetArray,

              MemRegion mr, bool is_zeroed);

   enum SomePublicConstants {

     // HeapRegions are GrainBytes-aligned

     // and have sizes that are multiples of GrainBytes.

     LogOfHRGrainBytes = 20,

     LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize,

     GrainBytes = 1 << LogOfHRGrainBytes,

     GrainWords = 1 <<LogOfHRGrainWords,

     MaxAge = 2, NoOfAges = MaxAge+1

   };

   enum ClaimValues {

     InitialClaimValue     = 0,

     FinalCountClaimValue  = 1,

     NoteEndClaimValue     = 2,

     ScrubRemSetClaimValue = 3,

     ParVerifyClaimValue   = 4

   };

   // Concurrent refinement requires contiguous heap regions (in which TLABs

   // might be allocated) to be zero-filled.  Each region therefore has a

   // zero-fill-state.

   enum ZeroFillState {

     NotZeroFilled,

     ZeroFilling,

     ZeroFilled,

     Allocated

   };

   // If this region is a member of a HeapRegionSeq, the index in that

   // sequence, otherwise -1.

   int hrs_index() const { return _hrs_index; }

   void set_hrs_index(int index) { _hrs_index = index; }

   // The number of bytes marked live in the region in the last marking phase.

   size_t marked_bytes()    { return _prev_marked_bytes; }

   // The number of bytes counted in the next marking.

   size_t next_marked_bytes() { return _next_marked_bytes; }

   // The number of bytes live wrt the next marking.

   size_t next_live_bytes() {

     return (top() - next_top_at_mark_start())

       * HeapWordSize

       + next_marked_bytes();

   }

   // A lower bound on the amount of garbage bytes in the region.

   size_t garbage_bytes() {

     size_t used_at_mark_start_bytes =

       (prev_top_at_mark_start() - bottom()) * HeapWordSize;

     assert(used_at_mark_start_bytes >= marked_bytes(),

            "Can't mark more than we have.");

     return used_at_mark_start_bytes - marked_bytes();

   }

   // An upper bound on the number of live bytes in the region.

   size_t max_live_bytes() { return used() - garbage_bytes(); }

   void add_to_marked_bytes(size_t incr_bytes) {

     _next_marked_bytes = _next_marked_bytes + incr_bytes;

     guarantee( _next_marked_bytes <= used(), "invariant" );

   }

   void zero_marked_bytes()      {

     _prev_marked_bytes = _next_marked_bytes = 0;

   }

   bool isHumongous() const { return _humongous_type != NotHumongous; }

   bool startsHumongous() const { return _humongous_type == StartsHumongous; }

   bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }

   // For a humongous region, region in which it starts.

   HeapRegion* humongous_start_region() const {

     return _humongous_start_region;

   }

   // Causes the current region to represent a humongous object spanning "n"

   // regions.

   virtual void set_startsHumongous();

   // The regions that continue a humongous sequence should be added using

   // this method, in increasing address order.

   void set_continuesHumongous(HeapRegion* start);

   void add_continuingHumongousRegion(HeapRegion* cont);

   // If the region has a remembered set, return a pointer to it.

   HeapRegionRemSet* rem_set() const {

     return _rem_set;

   }

   // True iff the region is in current collection_set.

   bool in_collection_set() const {

     return _in_collection_set;

   }

   void set_in_collection_set(bool b) {

     _in_collection_set = b;

   }

   HeapRegion* next_in_collection_set() {

     assert(in_collection_set(), "should only invoke on member of CS.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->in_collection_set(),

            "Malformed CS.");

     return _next_in_special_set;

   }

   void set_next_in_collection_set(HeapRegion* r) {

     assert(in_collection_set(), "should only invoke on member of CS.");

     assert(r == NULL || r->in_collection_set(), "Malformed CS.");

     _next_in_special_set = r;

   }

   // True iff it is or has been an allocation region in the current

   // collection pause.

   bool is_gc_alloc_region() const {

     return _is_gc_alloc_region;

   }

   void set_is_gc_alloc_region(bool b) {

     _is_gc_alloc_region = b;

   }

   HeapRegion* next_gc_alloc_region() {

     assert(is_gc_alloc_region(), "should only invoke on member of CS.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->is_gc_alloc_region(),

            "Malformed CS.");

     return _next_in_special_set;

   }

   void set_next_gc_alloc_region(HeapRegion* r) {

     assert(is_gc_alloc_region(), "should only invoke on member of CS.");

     assert(r == NULL || r->is_gc_alloc_region(), "Malformed CS.");

     _next_in_special_set = r;

   }

   bool is_reserved() {

     return popular();

   }

   bool is_on_free_list() {

     return _is_on_free_list;

   }

   void set_on_free_list(bool b) {

     _is_on_free_list = b;

   }

   HeapRegion* next_from_free_list() {

     assert(is_on_free_list(),

            "Should only invoke on free space.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->is_on_free_list(),

            "Malformed Free List.");

     return _next_in_special_set;

   }

   void set_next_on_free_list(HeapRegion* r) {

     assert(r == NULL || r->is_on_free_list(), "Malformed free list.");

     _next_in_special_set = r;

   }

   bool is_on_unclean_list() {

     return _is_on_unclean_list;

   }

   void set_on_unclean_list(bool b);

   HeapRegion* next_from_unclean_list() {

     assert(is_on_unclean_list(),

            "Should only invoke on unclean space.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->is_on_unclean_list(),

            "Malformed unclean List.");

     return _next_in_special_set;

   }

   void set_next_on_unclean_list(HeapRegion* r);

   HeapRegion* get_next_young_region() { return _next_young_region; }

   void set_next_young_region(HeapRegion* hr) {

     _next_young_region = hr;

   }

   // Allows logical separation between objects allocated before and after.

   void save_marks();

   // Reset HR stuff to default values.

   void hr_clear(bool par, bool clear_space);

   void initialize(MemRegion mr, bool clear_space, bool mangle_space);

   // Ensure that "this" is zero-filled.

   void ensure_zero_filled();

   // This one requires that the calling thread holds ZF_mon.

   void ensure_zero_filled_locked();

   // Get the start of the unmarked area in this region.

   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }

   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }

   // Apply "cl->do_oop" to (the addresses of) all reference fields in objects

   // allocated in the current region before the last call to "save_mark".

   void oop_before_save_marks_iterate(OopClosure* cl);

   // This call determines the "filter kind" argument that will be used for

   // the next call to "new_dcto_cl" on this region with the "traditional"

   // signature (i.e., the call below.)  The default, in the absence of a

   // preceding call to this method, is "NoFilterKind", and a call to this

   // method is necessary for each such call, or else it reverts to the

   // default.

   // (This is really ugly, but all other methods I could think of changed a

   // lot of main-line code for G1.)

   void set_next_filter_kind(HeapRegionDCTOC::FilterKind nfk) {

     _next_fk = nfk;

   }

   DirtyCardToOopClosure*

   new_dcto_closure(OopClosure* cl,

                    CardTableModRefBS::PrecisionStyle precision,

                    HeapRegionDCTOC::FilterKind fk);

 #if WHASSUP

   DirtyCardToOopClosure*

   new_dcto_closure(OopClosure* cl,

                    CardTableModRefBS::PrecisionStyle precision,

                    HeapWord* boundary) {

     assert(boundary == NULL, "This arg doesn't make sense here.");

     DirtyCardToOopClosure* res = new_dcto_closure(cl, precision, _next_fk);

     _next_fk = HeapRegionDCTOC::NoFilterKind;

     return res;

   }

 #endif

   //

   // Note the start or end of marking. This tells the heap region

   // that the collector is about to start or has finished (concurrently)

   // marking the heap.

   //

   // Note the start of a marking phase. Record the

   // start of the unmarked area of the region here.

   void note_start_of_marking(bool during_initial_mark) {

     init_top_at_conc_mark_count();

     _next_marked_bytes = 0;

     if (during_initial_mark && is_young() && !is_survivor())

       _next_top_at_mark_start = bottom();

     else

       _next_top_at_mark_start = top();

   }

   // Note the end of a marking phase. Install the start of

   // the unmarked area that was captured at start of marking.

   void note_end_of_marking() {

     _prev_top_at_mark_start = _next_top_at_mark_start;

     _prev_marked_bytes = _next_marked_bytes;

     _next_marked_bytes = 0;

     guarantee(_prev_marked_bytes <=

               (size_t) (prev_top_at_mark_start() - bottom()) * HeapWordSize,

               "invariant");

   }

   // After an evacuation, we need to update _next_top_at_mark_start

   // to be the current top.  Note this is only valid if we have only

   // ever evacuated into this region.  If we evacuate, allocate, and

   // then evacuate we are in deep doodoo.

   void note_end_of_copying() {

     assert(top() >= _next_top_at_mark_start,

            "Increase only");

     _next_top_at_mark_start = top();

   }

   // Returns "false" iff no object in the region was allocated when the

   // last mark phase ended.

   bool is_marked() { return _prev_top_at_mark_start != bottom(); }

   // If "is_marked()" is true, then this is the index of the region in

   // an array constructed at the end of marking of the regions in a

   // "desirability" order.

   int sort_index() {

     return _sort_index;

   }

   void set_sort_index(int i) {

     _sort_index = i;

   }

   void init_top_at_conc_mark_count() {

     _top_at_conc_mark_count = bottom();

   }

   void set_top_at_conc_mark_count(HeapWord *cur) {

     assert(bottom() <= cur && cur <= end(), "Sanity.");

     _top_at_conc_mark_count = cur;

   }

   HeapWord* top_at_conc_mark_count() {

     return _top_at_conc_mark_count;

   }

   void reset_during_compaction() {

     guarantee( isHumongous() && startsHumongous(),

                "should only be called for humongous regions");

     zero_marked_bytes();

     init_top_at_mark_start();

   }

   bool popular() { return _popularity == Popular; }

   void set_popular(bool b) {

     if (b) {

       _popularity = Popular;

     } else {

       _popularity = NotPopular;

     }

   }

   bool popular_pending() { return _popularity == PopularPending; }

   void set_popular_pending(bool b) {

     if (b) {

       _popularity = PopularPending;

     } else {

       _popularity = NotPopular;

     }

   }

   // <PREDICTION>

   void calc_gc_efficiency(void);

   double gc_efficiency() { return _gc_efficiency;}

   // </PREDICTION>

   bool is_young() const     { return _young_type != NotYoung; }

   bool is_scan_only() const { return _young_type == ScanOnly; }

   bool is_survivor() const  { return _young_type == Survivor; }

   int  young_index_in_cset() const { return _young_index_in_cset; }

   void set_young_index_in_cset(int index) {

     assert( (index == -1) || is_young(), "pre-condition" );

     _young_index_in_cset = index;

   }

   int age_in_surv_rate_group() {

     assert( _surv_rate_group != NULL, "pre-condition" );

     assert( _age_index > -1, "pre-condition" );

     return _surv_rate_group->age_in_group(_age_index);

   }

   void recalculate_age_in_surv_rate_group() {

     assert( _surv_rate_group != NULL, "pre-condition" );

     assert( _age_index > -1, "pre-condition" );

     _age_index = _surv_rate_group->recalculate_age_index(_age_index);

   }

   void record_surv_words_in_group(size_t words_survived) {

     assert( _surv_rate_group != NULL, "pre-condition" );

     assert( _age_index > -1, "pre-condition" );

     int age_in_group = age_in_surv_rate_group();

     _surv_rate_group->record_surviving_words(age_in_group, words_survived);

   }

   int age_in_surv_rate_group_cond() {

     if (_surv_rate_group != NULL)

       return age_in_surv_rate_group();

     else

       return -1;

   }

   SurvRateGroup* surv_rate_group() {

     return _surv_rate_group;

   }

   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {

     assert( surv_rate_group != NULL, "pre-condition" );

     assert( _surv_rate_group == NULL, "pre-condition" );

     assert( is_young(), "pre-condition" );

     _surv_rate_group = surv_rate_group;

     _age_index = surv_rate_group->next_age_index();

   }

   void uninstall_surv_rate_group() {

     if (_surv_rate_group != NULL) {

       assert( _age_index > -1, "pre-condition" );

       assert( is_young(), "pre-condition" );

       _surv_rate_group = NULL;

       _age_index = -1;

     } else {

       assert( _age_index == -1, "pre-condition" );

     }

   }

   void set_young() { set_young_type(Young); }

   void set_scan_only() { set_young_type(ScanOnly); }

   void set_survivor() { set_young_type(Survivor); }

   void set_not_young() { set_young_type(NotYoung); }

   // Determine if an object has been allocated since the last

   // mark performed by the collector. This returns true iff the object

   // is within the unmarked area of the region.

   bool obj_allocated_since_prev_marking(oop obj) const {

     return (HeapWord *) obj >= prev_top_at_mark_start();

   }

   bool obj_allocated_since_next_marking(oop obj) const {

     return (HeapWord *) obj >= next_top_at_mark_start();

   }

   // For parallel heapRegion traversal.

   bool claimHeapRegion(int claimValue);

   jint claim_value() { return _claimed; }

   // Use this carefully: only when you're sure no one is claiming...

   void set_claim_value(int claimValue) { _claimed = claimValue; }

   // Returns the "evacuation_failed" property of the region.

   bool evacuation_failed() { return _evacuation_failed; }

   // Sets the "evacuation_failed" property of the region.

   void set_evacuation_failed(bool b) {

     _evacuation_failed = b;

     if (b) {

       init_top_at_conc_mark_count();

       _next_marked_bytes = 0;

     }

   }

   // Requires that "mr" be entirely within the region.

   // Apply "cl->do_object" to all objects that intersect with "mr".

   // If the iteration encounters an unparseable portion of the region,

   // or if "cl->abort()" is true after a closure application,

   // terminate the iteration and return the address of the start of the

   // subregion that isn't done.  (The two can be distinguished by querying

   // "cl->abort()".)  Return of "NULL" indicates that the iteration

   // completed.

   HeapWord*

   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);

   HeapWord*

   oops_on_card_seq_iterate_careful(MemRegion mr,

                                    FilterOutOfRegionClosure* cl);

   // The region "mr" is entirely in "this", and starts and ends at block

   // boundaries. The caller declares that all the contained blocks are

   // coalesced into one.

   void declare_filled_region_to_BOT(MemRegion mr) {

     _offsets.single_block(mr.start(), mr.end());

   }

   // A version of block start that is guaranteed to find *some* block

   // boundary at or before "p", but does not object iteration, and may

   // therefore be used safely when the heap is unparseable.

   HeapWord* block_start_careful(const void* p) const {

     return _offsets.block_start_careful(p);

   }

   // Requires that "addr" is within the region.  Returns the start of the

   // first ("careful") block that starts at or after "addr", or else the

   // "end" of the region if there is no such block.

   HeapWord* next_block_start_careful(HeapWord* addr);

   // Returns the zero-fill-state of the current region.

   ZeroFillState zero_fill_state() { return (ZeroFillState)_zfs; }

   bool zero_fill_is_allocated() { return _zfs == Allocated; }

   Thread* zero_filler() { return _zero_filler; }

   // Indicate that the contents of the region are unknown, and therefore

   // might require zero-filling.

   void set_zero_fill_needed() {

     set_zero_fill_state_work(NotZeroFilled);

   }

   void set_zero_fill_in_progress(Thread* t) {

     set_zero_fill_state_work(ZeroFilling);

     _zero_filler = t;

   }

   void set_zero_fill_complete();

   void set_zero_fill_allocated() {

     set_zero_fill_state_work(Allocated);

   }

   void set_zero_fill_state_work(ZeroFillState zfs);

   // This is called when a full collection shrinks the heap.

   // We want to set the heap region to a value which says

   // it is no longer part of the heap.  For now, we'll let "NotZF" fill

   // that role.

   void reset_zero_fill() {

     set_zero_fill_state_work(NotZeroFilled);

     _zero_filler = NULL;

   }

 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \

   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);

   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DECL)

   CompactibleSpace* next_compaction_space() const;

   virtual void reset_after_compaction();

   void print() const;

   void print_on(outputStream* st) const;

   // Override

   virtual void verify(bool allow_dirty) const;

 #ifdef DEBUG

   HeapWord* allocate(size_t size);

 #endif

 };

 // HeapRegionClosure is used for iterating over regions.

 // Terminates the iteration when the "doHeapRegion" method returns "true".

 class HeapRegionClosure : public StackObj {

   friend class HeapRegionSeq;

   friend class G1CollectedHeap;

   bool _complete;

   void incomplete() { _complete = false; }

  public:

   HeapRegionClosure(): _complete(true) {}

   // Typically called on each region until it returns true.

   virtual bool doHeapRegion(HeapRegion* r) = 0;

   // True after iteration if the closure was applied to all heap regions

   // and returned "false" in all cases.

   bool complete() { return _complete; }

 };

 // A linked lists of heap regions.  It leaves the "next" field

 // unspecified; that's up to subtypes.

 class RegionList {

 protected:

   virtual HeapRegion* get_next(HeapRegion* chr) = 0;

   virtual void set_next(HeapRegion* chr,

                         HeapRegion* new_next) = 0;

   HeapRegion* _hd;

   HeapRegion* _tl;

   size_t _sz;

   // Protected constructor because this type is only meaningful

   // when the _get/_set next functions are defined.

   RegionList() : _hd(NULL), _tl(NULL), _sz(0) {}

 public:

   void reset() {

     _hd = NULL;

     _tl = NULL;

     _sz = 0;

   }

   HeapRegion* hd() { return _hd; }

   HeapRegion* tl() { return _tl; }

   size_t sz() { return _sz; }

   size_t length();

   bool well_formed() {

     return

       ((hd() == NULL && tl() == NULL && sz() == 0)

        || (hd() != NULL && tl() != NULL && sz() > 0))

       && (sz() == length());

   }

   virtual void insert_before_head(HeapRegion* r);

   void prepend_list(RegionList* new_list);

   virtual HeapRegion* pop();

   void dec_sz() { _sz--; }

   // Requires that "r" is an element of the list, and is not the tail.

   void delete_after(HeapRegion* r);

 };

 class EmptyNonHRegionList: public RegionList {

 protected:

   // Protected constructor because this type is only meaningful

   // when the _get/_set next functions are defined.

   EmptyNonHRegionList() : RegionList() {}

 public:

   void insert_before_head(HeapRegion* r) {

     //    assert(r->is_empty(), "Better be empty");

     assert(!r->isHumongous(), "Better not be humongous.");

     RegionList::insert_before_head(r);

   }

   void prepend_list(EmptyNonHRegionList* new_list) {

     //    assert(new_list->hd() == NULL || new_list->hd()->is_empty(),

     //     "Better be empty");

     assert(new_list->hd() == NULL || !new_list->hd()->isHumongous(),

            "Better not be humongous.");

     //    assert(new_list->tl() == NULL || new_list->tl()->is_empty(),

     //     "Better be empty");

     assert(new_list->tl() == NULL || !new_list->tl()->isHumongous(),

            "Better not be humongous.");

     RegionList::prepend_list(new_list);

   }

 };

 class UncleanRegionList: public EmptyNonHRegionList {

 public:

   HeapRegion* get_next(HeapRegion* hr) {

     return hr->next_from_unclean_list();

   }

   void set_next(HeapRegion* hr, HeapRegion* new_next) {

     hr->set_next_on_unclean_list(new_next);

   }

   UncleanRegionList() : EmptyNonHRegionList() {}

   void insert_before_head(HeapRegion* r) {

     assert(!r->is_on_free_list(),

            "Better not already be on free list");

     assert(!r->is_on_unclean_list(),

            "Better not already be on unclean list");

     r->set_zero_fill_needed();

     r->set_on_unclean_list(true);

     EmptyNonHRegionList::insert_before_head(r);

   }

   void prepend_list(UncleanRegionList* new_list) {

     assert(new_list->tl() == NULL || !new_list->tl()->is_on_free_list(),

            "Better not already be on free list");

     assert(new_list->tl() == NULL || new_list->tl()->is_on_unclean_list(),

            "Better already be marked as on unclean list");

     assert(new_list->hd() == NULL || !new_list->hd()->is_on_free_list(),

            "Better not already be on free list");

     assert(new_list->hd() == NULL || new_list->hd()->is_on_unclean_list(),

            "Better already be marked as on unclean list");

     EmptyNonHRegionList::prepend_list(new_list);

   }

   HeapRegion* pop() {

     HeapRegion* res = RegionList::pop();

     if (res != NULL) res->set_on_unclean_list(false);

     return res;

   }

 };

 // Local Variables: ***

 // c-indentation-style: gnu ***

 // End: ***

 #endif // SERIALGC